Probiotics last about 48 hours in your gut before your own microbiome out competes them and they die off. That's why you need to have another everyday.
Just get a fecal matter transplant and kick-start off a whole new microbiome from a healthier person.
Honestly, it's fairly safe. A probiotic food is already colonized/being eaten by micro-organisms and they want to keep other micro-organisms out. I've eaten a cup of yogurt that was a year past it's expiration date and only noticed because it was so tangy.